Indium tin oxide (ITO) has been the most commonly used material as a transparent electrode for flat panel displays. However, it has some drawbacks: it cannot be used for flexible displays which is the next generation of display due to its brittle nature, as well as the dwindling supply of indium.
Recently, nanomaterials such as metallic silver (Ag) nanowires, carbon nanotubes (CNT) and graphene have been investigated as potential replacement materials for transparent electrodes on flexible substrates instead of ITO. A number of studies have been carried out using a network of Ag nanowires as an electrode material. However, the cost of Ag itself is high and is comparable with the cost of ITO. On the other hand, copper (Cu) is an abundant and cheap material, and is the dominant metal used as an electrical conductor. It has a high electrical conductivity and is used as an electrode in conventional electronics. Though it has many advantages, Cu cannot be used as a transparent electrode in its current form due to some of the reasons as listed below.                It is difficult to use Cu with other materials because Cu usually reacts with other metals very aggressively to form intermetallic compounds which degrade its properties.        Cu oxidizes in ambient condition, and more severely at higher temperatures. The melting temperature of Cu (1084° C.) is much higher than the processing temperature (<250° C.) of transparent electrodes on typical flexible substrates, e.g., Polyimide (PI, Tg:340° C.), Polycarbonate (PC, Tg:156° C.), Polyethersulfone (PES, Tg:223° C.), Polyethyleneterephthalate (PET, Tg:78° C.), Polyethylenenaphthalate (PEN, Tg:121° C.), Polyarylate (PAR, Tg:350° C.).        